Alkanolamides perform a variety of functions including viscosity enhancement, foam stabilization, emulsification and detergency. Specific applications include as humectants and hair detanglers. Chemically, alkanolamides are the reaction product of an alkanolamine and a fatty material. Fatty materials are a class of compounds which include fatty carboxylic acids, fatty methyl esters and fatty glycerides. Sources of fatty materials include coconut, peanut, soybean, and rapeseed oils, fractionated and non-fractionated fatty methyl esters and fatty acids of carbon chains of varying lengths.
Variations in carbon chain lengths of the fatty sources can change the properties of alkanolamides. For example, a finished product having as an ingredient C8 to C10 fatty acids exhibit foam stability, but contribute little as thickeners. C12 to C14 fatty acids are particularly useful as foam boosters; they also show good viscosity building properties. Blending alkanolamides of differing carbon chain lengths can help optimize performance of the finished products in which they are incorporated. Lauric-myristic diethanolamides, for example, are common ingredients in formulations of high foaming products such as dishwashing detergent, bubble bath and hair shampoo. They also impart emolliency and conditioning effects to skin and hair, making them among the most commonly used alkanolamides in the personal care industry.
Higher molecular weight, unsaturated fatty alkanolamides reduce foam and produce good viscosity build. Illustrative are oleic and linoleic alkanolamides which are excellent viscosity builders at low concentrations. This property makes them particularly useful in surfactant-containing formulations that otherwise are difficult to thicken. Higher molecular weight unsaturated products, however, are known to be oxidatively unstable and can interfere with fragrance in finished products.
Shea butter is a butter extracted from the kernel of Butrospermum parkii. This plant, also referred to as Vitellaria paradoxa, is native to Africa. The term butter describes a material that is a solid at room temperature, but melts at about 40° C. Chemically, shea butter is a triglyceride conforming to the following structure
wherein Ra, Rb and Rc each have one of the following compositions:
R GroupCommon NameRange (%)Typical (%)C11H23Lauryl0.1–2.00.2C13H27Myristyl0.5–2.01.0C15H31Cetyl2.0–6.04.0C17H35Stearyl25.0–50.035.0C17H33Oleyl40.0–60.059.0C17H31Linoleyl0.5–1.00.8
The average composition of Rb is different than Ra and Rc, the latter two being similar. The Rb moiety contains predominantly the unsaturated C18 group (oleyl) while Ra and Rc contain predominantly the saturated C18 group (stearyl). Differences between internal (Rb) and terminal (Ra, Rc) substitution are seen in natural products but not in synthetic molecules produced in the laboratory.
The high levels of stearyl and oleyl groups make shea butter and its alkanolamide derivatives of particular interest in the personal care industry. While other raw materials used in personal care products have these species, the compounds of the present invention have significantly high concentrations of unsaponifiables, which posses highly desired antioxidant, ultra-violet radiation protection, and free-radical scavenging properties. MPSB of the present invention typically contains from about 5% to about 15% by weight of unsaponifiables. In contrast, other butters commonly used in personal care products have less than 2% unsaponifiables. For example, coca butter (from Theobroma cacao) averages 0.4% unsaponifiables and Illipe butter (from Shorea stenoptera) averages 1.1%.
As described in greater detail below, the novel shea butter alkanolamide compounds of the present invention are produced by reacting shea butter, preferably MPSB, with an alkanolamine, preferably under specific mild processing conditions. By “mild processed” is meant processes that do not remove or otherwise diminish the amount or potency of active ingredients, particularly highly desired unsaponifiables. In one aspect of the present invention, mild processing is employed both at the time of harvesting and initial extraction (creating mild-processed shea butter) and during subsequent preparation of derivatives. These mild processes result in materials containing unexpectedly high amounts unsaponifiables, notably antioxidants.
Prior art alkanolamides do not possess the antioxidant and free-radical scavenging properties of compounds of the present invention. For example, U.S. Pat. No. 5,741,916 discloses the use of meadowfoam seed oil to make alkanolamides. The materials described in the '916 patent do not possess the desirable unsaponifiable fractions which are present in the alkanolamides of the present invention.
The shea butter alkanolamides of the present invention thus deliver unexpectedly high amounts of unsaponifiables to the skin and hair in a heretofore unachievable manner. They not only thicken but also act as antioxidants and free radical scavengers.